An AP atlas and axis projection with poor positioning demonstrates the upper incisors about 1 inch (2.5 cm) inferior to the posterior occiput, obscuring the dens and atlantoaxial joint. How was the positioning setup mispositioned for such a projection to be obtained?
1)The patient's face was rotated toward the left side.
2)The acanthiomeatal line was perpendicular to the IR, and the central ray was perpendicular.
3)The patient's chin was tucked more than needed.
4)An imaginary line connecting the occlusal plane and posterior occiput's inferior edge was not aligned perpendicular to the imaging table.
A) 1 only
B) 2 only
C) 2 and 3 only
D) 2, 3, and 4 only

Question

Quizplus · Accepted Answer

Option 2 is correct as the acanthiomeatal line (AML) should be parallel to the IR, and the CR should be perpendicular. However, option 3 is incorrect as the patient's chin should be tucked in to avoid superimposition of the mandible and cervical spine, which does not affect the position of the upper incisors. 
Option 4 is also correct as the alignment of an imaginary line connecting the occlusal plane and posterior occiput's inferior edge should be perpendicular to the imaging table, which helps in visualizing the dens and atlantoaxial joint. 
Option 1 is incorrect as the rotation of the patient's face would cause distortion in the image, but it would not affect the position of the upper incisors 1 inch inferior to the posterior occiput.

An AP Atlas and Axis Projection with Poor Positioning Demonstrates